The present invention relates to a disk clamping device suitable for use in a disk player capable of reproducing a selected alternative one of a compact disk and a video disk.
Optical systems for reproducing a compact disk and an optical video disk have the same general arrangement. So-called compatible disk players capable of playing either a compact disk or an optical video disk have been developed and marketed. A compact disk has a small thickness and relatively small outer diameter and center hole diameter compared with a video disk. A video disk thus has a much larger mass than a compact disk.
One type of conventional compatible disk player has been provided with separate turntables for playing compact and video disks, while a single pickup is used commonly for the two types of disk. This disk player, however, has a generally very complicated structure. For this reason, a compatible disk player employing only a single turntable has been developed.
In such a conventional disk player employing a single turntable for both types of disks, the same pressing surface of a magnetic clamper is used for pressing and clamping both types of disk against the turntable. However, due to the difference in thickness between compact and video disks and the resulting difference in distance between the clamper and associated magnet, the clamping force for a video disk is significantly weaker than for a compact disk, even though the video disk is of much greater mass than the compact disk and thus actually should be clamped with a greater clamping force.